Medical language has a vocabulary and style that takes some effort for a novice to replicate, plus ensure all the necessary x-rays, lab tests, nurse, physio, occupational therapy notes are there. Could easily be a few dozen pages all told. I expect someone at an insurance company that was used to reading these types of records would pick up on this pretty quickly.

IIRC, dismemberment insurance doesn't specify how many you're SUPPOSED to have. Say you did have a useless third arm, and lost it in an accident, would you get payola? You're disabled for life, with only two good arms left...